The spread of services that utilize networks has been accompanied by an increasing demand for facility improvements of networks to be carried out such that the quality state of a network is confirmed, and service users are able to comfortably utilize a service. Indexes that confirm the quality state of a network include, for example, a usable bandwidth, a round-trip delay time, a packet loss rate, and fluctuation of a packet arrival interval.
In Patent Document 1, disclosed is a technique that confirms a usable bandwidth of a network. Specifically, according to the technique disclosed in Patent Document 1, a usable bandwidth is estimated by transmitting from a transmission side a plurality of measurement packets (packet train) having a gradually increasing or decreasing packet size at a fixed transmission interval, and then comparing the transmission interval to a reception interval on a reception side. However, the usable bandwidth is the only index that can be estimated by the technique disclosed in Patent Document 1, and it is not possible to measure a round-trip delay time.
In Patent Document 2, disclosed is a technique that calculates a usable bandwidth and a round-trip delay time as a result of a packet train making a round-trip between two communication devices. Furthermore, in Patent Document 3, disclosed is a technique that calculates a round-trip delay time based on a transmission time point and a reception time point of a measurement packet, and a transmission time point and a reception time point of a return packet.